1. Field of the Invention
The present invention relates to light-sensitive image recording materials and particularly, to those which utilize an intermolecular reaction which occurs between two kinds of polymers. More specifically, it relates to dry processes for recording light images using such recording materials.
2. Description of the Prior Art
In the past silver halide light-sensitive materials, diazo light-sensitive materials and the like have been mainly employed as light-sensitive image recording (photographic) materials. However, these materials require exclusively a wet development processing. Numerous attempts to record images using dry processing, for instance, by heat development, have been made in recent years for the purpose of elimination of the disadvantages inherent in wet development processes. For instance, materials such as heat developable light-sensitive materials [one example of which is commercially available under the tradename of "Dry Silver" (produced by 3M Co.)] utilizing a silver salt of a fatty acid, heat developable diazo light-sensitive materials, light-sensitive materials utilizing organic tellurium compounds (as disclosed in, for example, British Pat. No. 1,405,628) and so on have been developed. These light-sensitive materials, unfortunately, have their own defects. Namely, materials using silver salts of fatty acids are expensive because silver is employed therein and a large amount of skill is required to prepare such a light-sensitive material. Toxicity is a problem in light-sensitive materials containing organic tellurium compounds since they are toxic, and heat developable diazo light-sensitive materials tend to fog upon storage and are unstable.
On the other hand, it is known that halogen-containing high polymers such as polyvinyl chloride, polyvinylidene chloride and the like undergo a dehydrohalogenation due to the interaction of light or heat to produce conjugated polyenes and thereby, a color is formed. A number of studies have been made on this reaction mainly from the standpoint of stabilization of halogen-containing high polymers, and recent results of this research are summarized in G. Ayrey, B. C. Head and R. C. Poller, "Macromolecular Reviews", J. Polymer Sci: Macromolecular Reviews, volume 8, page 1 (1974). Light-sensitive image recording materials taking advantage of the lability of halogen-containing high polymers and particularly, the property that they can be changed to polyenes and thereby, become colored, were proposed in Japanese Patent Publications Nos. 10647/75 and 35451/76; U.S. Pat. Nos. 3,615,456; 2,772,159; 3,046,136; 3,155,513; 2,712,996 and 2,754,210; and S. B. Elliot, Photographic Eng., volume 4, page 133 (1953). In each of these light-sensitive image recording materials, polyene images are produced by employing materials which are capable of accelerating the dehydrohalogenation reaction which halogen-containing high polymers undergo due to the interaction of light (e.g., metallic oxides) with the halogen-containing high polymers, exposing the recording materials to light and optionally, by heating. Since light-sensitive image recording materials of this kind primarily utilize, however, the lability of halogen-containing high polymers, achieving a stabilization of the light-sensitive materials and an increase in sensitivity to light simultaneously has been regarded as technically difficult if not technically opposed.
Now, in a prior application we discovered that heat-sensitive coloring compositions comprising solid mixtures of basic polymers, such as polyvinyl pyridines, and halogen-containing high polymers, such as polyvinylidene halides, were colored brownish-black by heating, as disclosed in Japanese Patent Application No. 16369/77 (corresponding to U.S. patent application Ser. No. 878,351, filed Feb. 16, 1978).
It was found therein that coloration was not observed in practice when only polyvinylidene halides were heated (e.g., at a temperature of 100.degree. to 200.degree. C.). Accordingly, it was thought that the thermal coloration of the above-described solid mixtures in part involved an intermolecular reaction between different polymers (presumably corresponding to an acceleration of the dehydrohalogenation reaction of polyvinylidene halides by capture of hydrogen halides using the polyvinyl pyridines).
Therefore, the above-described heat sensitive coloring compositions are quite stable at temperatures in the vicinity of room temperature (25.degree. C.), and can be stored for a long time without fogging occurring. On the other hand, coloration can proceed with a practically sufficient speed only after affirmative heating (up to, for instance, a temperature higher than the glass transition points of the polyvinyl pyridines used).
Moreover, the thus produced colored materials are considered to be composed of "polyenes", as such are defined in Japanese Patent Application No. 16369/77, and the colored materials are quite stable to external stimuli such as light, heat, moisture and so on.